1. Field of the Invention
The present invention generally relates to an oil pump apparatus including an oil pump and a control valve for controlling the flow of oil back to a suction port of the oil pump.
2. Description of the Prior Art
A conventional oil pump apparatus installed on a vehicle engine is disclosed in Japanese Utility Model laid open No. 61 (1986)-23485. The oil pump apparatus disclosed in this publication includes an oil pump and a control valve through which flows a portion of oil (a portion of the oil exceeding the quantity of the oil consumed at a component to which the oil is supplied) pumped out from the oil pump back to a suction port of the oil pump, an oil pan, an oil reservoir, an oil tank and so on, in order to reduce a load applied to the oil pump at a medium and high rotation speed ranges of the oil pump.
In accordance with the above device, when a plurality of components, at least one of which is an actuator operated by the oil pressure generated by the oil pump (e.g., an actuator applied to a variable valve timing mechanism or a variable valve lift mechanism of the engine) are connected to the oil pump, only the excess oil exceeding the quantity of the oil consumed at all components (including an operating actuator) is returned to the suction port of the oil pump even though the actuator is not operated. Therefore, a large amount of the oil which is unnecessary to the components is supplied to the components when the actuator is not operated.